You are welcome for sure. Let me know---- if it changes or goes away in the next couple of days or stays the same! We'll go from there.
So, you maybe have an infected cyst? Sometimes people get lymph nodes under their arm pit but those are usually smaller, not visible to the eye and don't hurt. This is painful which indicates perhaps a clogged hair follicle or a cyst. Leave it alone as your fingers could infect it more. You could try a warm compress on it to see if a head forms. But overall, if it doesn't go away, a trip to the doctor would make sense. Please come back and tell me what the doctor says or what happens with it!